1. Field of Invention
This invention relates to a rotating apparatus and, in particular, to a magnetic bearing structure.
2. Description of the Related Art
In a conventional bearing for supporting a rotor to rotate, a sleeve bearing as shown in FIG. 1 is adopted. A pair of sleeves 10 is provided in the radial direction. The rotor is in direct contact with the bearing while rotating; thus friction, noise, and vibration are generated. This increases the power consumption and lowers the lifetime of the bearing. Since the rotation speed cannot be increased, the lower rotation speed cannot meet the high vacuum requirement of a vacuum system. Moreover, the lubricant between the rotor and the bearing is likely to be squeezed out when the rotor rotates, therefore, it cannot meet a highly clean environment requirement, e.g., in a clean room.
To overcome the above problems about friction, rotation speed, lifetime, and cleanness, magnetic suspension has been widely used in some industries for supporting rotors in a non-contact way. Using the frictionless feature of the magnetic bearing, the rotation speed can be increased and this can be applied in semiconductor manufacturing equipment that needs high speed rotating vacuum apparatuses to meet the requirements of processes to be proceeded in high vacuum states. It can also be applied in the fan motor of a ventilating device in a computer system. By increasing the rotation speed of the fan motor, the convection efficiency can be increased. Also, since the magnetic bearing supports the rotor by the magnetic force, lubricant is not needed. This can avoid environmental contamination by the lubricant for use in a conventional rotor. Thus, the invention can be applied in the carrier system or manufacturing apparatuses in a clean room of high cleanness.
Referring to FIG. 2, a conventional magnetic bearing structure of a high speed rotating device comprises a bearing base 20, a set of coils 30 around a stator 40 mounted on the bearing base 20, and a rotation shaft 50 made of a permanent magnet mounted on a rotor 60. When the coils 30 are excited with an electrical current, the rotor 60 rotates with respect to the stator 40. The conventional magnetic bearing structure consists of five sets of bearings. The axial direction (z-axis) is provided with a set of thrust magnetic bearings 70 made of permanent magnets. The upper and lower sides in the radial direction (x-axis and y-axis) are provided with radial magnetic bearings 80, 90 (not shown) made of permanent magnets. They are controlled independently in five axial directions. In particular, the position of the rotor 60 in the radial direction is controlled by the bearings 80, 90. When the rotor 60 deviates from its equilibrium position, the magnetic repulsion generated by the permanent magnets in the opposite directions pushes the rotor 60 back to its equilibrium position. A magnetic clearance kept by the magnetic repulsion between the rotor 60 and the bearings 70, 80, 90 prevents the bearings from direct contact with the rotor while keeping the rotor in equilibrium. The friction between the rotor 60 and the bearings 70, 80, 90 can be avoided and therefore the noise and vibration caused by friction become less. In addition, the conventional magnetic bearing structure can lower the power consumption, and increase the rotation speed of the rotor 60 and the lifetime of the bearings.
However, in this conventional magnetic bearing structure, the bearings are controlled independently in five axial directions and the bearings have to be handled in five axial directions during manufacturing and assembling. Therefore, it is considered that the structure is complicated and incurs a high manufacturing cost.
An object of this invention is to provide a magnetic bearing structure, which utilizes non-contact magnetic force to control the position of a rotor to avoid friction, to lower noise, vibration and power consumption, to increase the rotational speed and the lifetime of the bearing, and to lower the manufacturing cost.
In a preferred embodiment of the invention, a magnetic bearing structure is provided. This structure modifies the conventional five sets of independently controlled bearings into a set of bearing so as to control the position of the rotor in both the radial direction and the axial direction. The set of bearing can be used in a high speed rotating device, which comprises a bearing base, a set of coils around a stator mounted on the bearing base, and a rotation shaft on a rotor. When the set of coils is excited with an electrical current, the rotor rotates in relation to the stator. Moreover, the magnetic bearing structure comprises: a magnetic shaft attachment in a convex form and fixed on the outer side of the rotation shaft, and a magnetic stator attachment in a concave form and fixed on the inner side of the stator, wherein the magnetic bearing structure is used to control a position of the rotor in both a radial direction and an axial direction by repulsive magnetic forces produced between the magnetic shaft attachment and the magnetic stator attachment.
Another preferred embodiment of this invention provides a magnetic bearing structure. This structure modifies the conventional five sets of independently controlled bearings into a set of bearing so as to control the position of the rotor in both the radial direction and the axial direction. The set of bearing can be used in a high speed rotating device, which comprises a bearing base, a set of coils around a stator mounted on the bearing base, and a rotation shaft on a rotor. When the set of coils is excited with an electrical current, the rotor rotates in relation to the stator. Moreover, the set of bearing comprises: a magnetic shaft attachment in a concave form and fixed around the outer side of the rotation shaft, and a magnetic stator attachment in a convex form and fixed on the inner side of the stator, wherein the magnetic bearing structure is used to control a position of the rotor in both a radial direction and an axial direction by repulsive magnetic forces produced. between the magnetic shaft attachment and the magnetic stator attachment.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.